Development of adequate dosage regimens for the neuroleptics has been hampered by a paucity of information concerning their pharmacokinetics. The formation of neuroleptic metabolites with varying degrees of activity further complicate the interpretation of blood drug concentrations. The Neuroleptic Dopamine Receptor Assay is a newly developed analytical procedure that allows measurement of drug activity rather than just drug concentration. It will therefore allow quantitation of the parent drug and all active metabolites. This study will investigate the use of this assay for the characterization of the pharmacokinetic profiles of haloperidol, chlorpromazine, thioridazine, trifluoperazine, and thiothixene in normal healthy volunteers. These data will be important for future studies and for the development of improved dosage regimens.